This science project requires purchasing bottled skunk scent. Do not use a live skunk! See the Materials and Equipment list for details.

Cost

Average ($40 - $80)

Safety

Skunk odor has a very strong smell that can cause nausea and vomiting. This project must be done in a well-ventilated outdoor area. Eye protection and protective clothing are required to avoid contact with skin and eyes.

Abstract

Have you or one of your pets ever been sprayed by a skunk? Hopefully not, but if you have, you probably know that the smell can be very unpleasant and hard to get rid of. There are many "folk remedies" for getting rid of skunk scent, but if you ever do get sprayed by a skunk, how will you know which one to try? In this science project, you will test the ability of various mixtures to remove the bad scent from rags that have been contaminated with bottled skunk scent, and determine which one works the best.

Objective

Investigate the ability of various mixtures to remove skunk odor from test rags.

Credits

Ben Finio, PhD, Science Buddies

This science project idea is adapted from a 2012 project submitted to Science Buddies by Kate Lande while she was a student at the McMurray Middle School in Vashon Island, WA.

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Introduction

Hopefully you (or your pets) have never had the unpleasant experience of being sprayed by a skunk (Figure 1). The scent of a skunk can be very strong and hard to get rid of. You may have heard of various remedies—such as washing your dog with lemon or tomato juice—but do you know if it is a scientifically tested treatment, or just an old folk tale with no scientific evidence to back it up? In this science project, you will do an experiment to test the ability of different mixtures to remove skunk odor from test rags. Before you do this, it will help to understand the chemistry of skunk odor.

Figure 1.
A striped skunk. Skunks can spray a very smelly odor when they feel threatened, and the scent can be quite difficult to get rid of.

Skunk odor smells so bad to us because it contains thiols. Thiols are chemical compounds that contain sulfur and hydrogen. There are many different types of thiols and some of them have strong, unpleasant odors (for example, rotten eggs and flatulence). Although we usually do not like them, one positive use for thiols is as an additive to natural gas (which is odorless), because the unpleasant odor warns people of gas leaks. There are also thiols that smell good to most people, like those in grapefruit and roasted coffee.

One way that the thiol odor can be destroyed is by changing the thiol chemical compound into a different chemical compound, which may not smell at all. This can be done using a chemical process called oxidation. Oxidation happens when an oxidizing agent interacts with a chemical compound (such as a thiol) and steals electrons from that compound. As their name implies, oxidizing agents often contain oxygen, and some examples include oxygen itself (O2) and hydrogen peroxide (H2O2). Oxidation can change the chemical structure of a chemical compound, thus lessening or removing a thiol's bad smell. In this chemistry science project, you will test the ability of four different mixtures, each common home remedies, to remove skunk odor from a material:

Dish soap and water: The combination of dish soap and water is not a notable oxidizing agent, but it is a common cleaning solution called a surfactant. Soap molecules help surround dirt and stain molecules and carry them into the water, which can then be rinsed out of the material.

Tomato juice: Tomato juice is a mild oxidizing agent because it contains small amounts of malic and citric acids. Acids usually (but not always) act as oxidizing agents. To learn more about acids, check out the Science Buddies resource on
Acids, Bases & the pH Scale.

Vinegar: Vinegar is a mild oxidizing agent that contains acetic acid.

Hydrogen peroxide, baking soda, and dish soap: This combination contains two different oxidizing agents (hydrogen peroxide and baking soda) and a surfactant (dish soap), and is a popular remedy developed by a chemist in the 1990s (see the Bibliography section to learn more).

Which one do you think will be the most successful at removing skunk odor?

Terms and Concepts

Thiol

Chemical compound

Oxidation

Oxidizing agent

Surfactant

Acid

Questions

What causes skunk odor to smell so bad?

Are there other substances that smell bad for the same reason?

What chemical process can remove the smell from skunk odor? What actually occurs during this process?

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Materials and Equipment

Bottled skunk scent, available from sports and outdoor stores and online retailers like
Amazon.com.

Disposable, protective clothing that you do not mind throwing away when the experiment is over (for example, an old long-sleeve shirt and pair of pants)

Additional protective gear: rubber gloves, shower cap, safety goggles

Medicine dropper

Measuring teaspoon

Measuring cup, 1/4 cup

Plastic buckets (4)

Permanent marker

Cloth rags (5)

Water (1 liter)

Liquid dish detergent (2 teaspoons)

Tomato juice (1 liter)

Vinegar (1 liter)

Hydrogen peroxide, 3% concentration (1 liter)

Baking soda (1/4 cup)

Wooden paint mixing sticks (6), available at hardware stores

Timer

Hose for rinsing

Plastic garbage bag to get rid of disposable materials

Adult volunteers (at least 3) to act as "smell testers". The volunteers should stay away from the testing area until you are ready to do the smell tests so they do not get used to the smell.

Well-ventilated outdoor area to work, as far away from your house and other people as possible

Lab notebook

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Experimental Procedure

Use the permanent marker to label your four plastic buckets A, B, C, and D.

Mix or pour the substances below into each bucket. Be sure to stir the mixtures that include more than one material. Use a new wooden paint stick to mix each bucket that requires mixing so you do not cross-contaminate your mixtures.

It is time to get out the skunk odor. Remember to make sure that you are in a well-ventilated outdoor area. Keep your volunteer smell testers away from the test area for now, as their noses need to be fresh when they do the testing (meaning, you do not want them to get used to the skunk scent while you are doing your experiment).

Warning: Remember that the smell of skunk odor is very strong. If at any time you feel nauseous, dizzy, or develop a headache, stop the experiment, put the lid back on the skunk scent, and move to a different well-ventilated outdoor area, away from your experiment. Do not sniff the undiluted skunk scent directly from the bottle.

Using the medicine dropper, place 10 drops of skunk odor onto each rag. Important: How you place the drops could affect the results of your experiment; for example, if you put all 10 drops in the same place, or space all 10 drops out evenly across the rag. The important thing is to be consistent and use the same method to apply the drops to each rag.

Place rags A, B, C, and D into their corresponding buckets. Do not put rag X in a bucket; this is your control rag.

Use a new wooden paint stick to swish each rag around in its bucket for 1 minute, then let all of the rags soak for 15 minutes. Remember to use a different paint stick for each bucket so you do not cross-contaminate your samples. When you are done swishing, keep each paint stick next to the bucket in which it was used.

Use the paint sticks from step 9 to remove each rag from its bucket, and rinse them using the hose. Be sure to rinse each rag the same way and for the same amount of time (for example, 15 seconds each). Do not rinse the control rag. Important: Thoroughly rinse your rubber gloves with the hose in between rags, to help prevent cross-contamination.

Have your adult volunteers smell each rag, and rate them on a scale of 0–10, where 0 means the rag does not smell at all, and 10 means the smell is almost unbearable. Have them smell the control rag, X, last, since it will smell the strongest; you do not want them to be overwhelmed by the strong smell and then be unable to rate the other rags. Record their ratings in your lab notebook. You could use a data table to keep track of your results.

Important: When using human volunteers for a science project many science fairs require you to get a signed piece of paper, called informed consent, saying that the volunteers know what they are signing up for and agree to it. This is an important step that research scientists always have to do when human volunteers are involved. You can read more about Projects Involving Human Subjects here. Also make sure to check with your teacher or science fair coordinator.

Rag

Remedy

Volunteer 1,Smell (scale of 0–10)

Volunteer 2,Smell (scale of 0–10)

Volunteer 3,Smell (scale of 0–10)

A

Water + dish soap

B

Tomato juice

C

Vinegar

D

Hydrogen peroxide + baking soda + dish soap

X

None

Table 1. A data table to keep track of the results of your experiment.

Optional: If possible, and if your volunteers are willing, you can wait 30 minutes, then have them each smell and re-rate the rags. Record the results, and see if everyone rated the rags the same as the first time.

Once you have finished recording all your data, use the plastic trash bag to dispose of all the disposable materials from the experiment. Store the bag outside until it can be collected.

You may want to create a bar graph to help compare your results, with mixture on the x-axis and smell rating on the y-axis. You could average the ratings of your three volunteers, or graph their ratings individually (or both).

Analyze your data by rating the remedies from best to worst. Which one resulted in the lowest smell rating on the 0–10 scale? Did strong oxidizing agents work better than weak oxidizing agents, or remedies that did not have oxidizing agents at all?

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Variations

Can you think of additional treatments to test besides the ones listed in this science project?

The combination of hydrogen peroxide, baking soda, and dish soap is a popular remedy. You already tested dish soap (mixed in water) by itself; what happens if you test hydrogen peroxide alone, or baking soda mixed in water? Are these ingredients just as effective on their own?

Can you think of another scent source besides skunk odor? The Introduction mentioned that some things contain thiols, but smell good. Test those and find out if the same remedies still work.

What happens if you change the amount of time the rags soak in each mixture? Does it work better if you leave them overnight?

Pick your best working remedy and test it at lower concentrations (meaning, use more water or less of the cleaning material). Does it still work at lower concentrations? What is the minimum concentration required to effectively remove the smell?

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Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

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